Yes you can and it should work on all operating systems.
When you plug in an external microphone or webcam, you can select them as input sources on Clipchamp's webcam recording screen in the bottom right by clicking on the gear icon.
Please see the 2nd part of this article for a brief explanation of how external microphones work with Chromebooks, which is slightly different to how they work when using Clipchamp on a Mac or Windows PC.
Note that we recently updated some elements of the layout of the webcam recording user interface. The screenshots below show the interface of a previous version, however the camera and microphone options are still accessible in the bottom right corner of the webcam window and the same principles as described in this article apply to the latest version of Clipchamp.
1) On Mac and Windows
When you plug a USB camera into your computer, it will automatically get recognised by your operating system and appear as a camera and (if it has one built in) microphone input option in Clipchamp's webcam recording interface. All you have to do is select the camera and microphone you'd like to use as your video and audio source from the menu options.
2) On Chromebooks
Any external microphone you plug into a Chromebook is likely to get automatically selected by Chrome OS as the default mic in the Chromebook's audio settings as soon as you plug it in.
That was the case when we tested it on a Toshiba Chromebook (2014 model) so we're assuming that this is the default behavior on other Chromebook models as well.
Unlike on Mac or Windows, the external microphone won't appear as a separate microphone to select in Clipchamp but the "default" option in there is your external mic as long as it was selected by Chrome OS in the audio settings.
You can test that by following these steps:
Click on the Clock/Wifi/Battery indicator on the right side of the task bar, then go to audio settings by clicking on the arrow next to the volume slider
Make sure that your external mic is selected as the default microphone
If it is that means that Clipchamp will record audio through it even though it does not appear in the dropdown on Clipchamp's webcam recording screen. The "default microphone" on that screen is your external mic.
Please note that Chromebooks don't seem to be able to record video and audio from the Lifecam (and its inbuilt mic) at the same time. This works on other computers (Mac, Windows) but not on Chromebooks, at least not during our testing.
During the testing, ChromeOS was either able to record audio OR video from an external USB source (such as the Lifecam) but not both at the same time from the same source.
What we ended up doing was select the Chromebook's inbuilt mic as the audio source in the ChromeOS settings, after which we could pick the Lifecam as the video source in Clipchamp.